Electronic equipment which is to be located outdoors and placed within a housing structure to protect the equipment from mother nature, generally requires some method of regulating or controlling the internal temperature of the housing and the temperature of the electronic components. It is well known that the reliability of electronic components decreases significantly if they are subjected to high temperature extremes or to large temperature swings, especially if these swings or cycles are frequent. These temperature cycles can be due for example to electronic loading (e.g. peak telephone traffic times) or seasonal day-night temperature differences.
Conventional convection methods of temperature regulation within equipment housings have relied on maintaining internal ambient air temperatures within a predetermined range and to provide an airflow over the equipment to assist in the removal of component heat by an air medium. Component manufacturers have specific temperature ranges within which they guarantee their components will function reliably. A semi conductor component junction temperature range stated by a manufacturer will typically be in the range of -15.degree. C. to +85.degree. C. Generally speaking suppliers of electronic equipment will stipulate that their equipment (incorporating semi conductor components) if operated within a commercial operating zone (ambient temperature internal to a housing for example) of typically 0.degree. C. to +50.degree. C. will operate reliably. In other words operating their equipment in this commercial operating zone will ensure that component junction temperatures (-15.degree. C. to +85.degree. C.) set by component manufacturers will not be exceeded.
Service providers often provide air-conditioning units and or heating elements which are then thermostatically controlled. While this form of convection cooling (or heating) tends to be satisfactory for equipment housings which are either indoors or outdoors and in close proximity to electrical power, it is not an acceptable method for remote outdoor housing applications. Typical data communications cabling is not of sufficient size (gauge) to handle the power required by air-conditioning units or heating elements and hence at great expense, separate power cables must therefore be run out to the remote location. The ongoing year after year energy costs required to power such air-conditioning units and/or heating elements can also be significant. More importantly, it is generally accepted that if any degree of system reliability is to be realized, backup power systems (batteries/generators etc.) along with backup air-conditioning units and heating elements must be provided. These costs, all of which can be very significant, ultimately cut into profit margins of the equipment owners. In addition any breakdown in the heating and cooling equipment may result in disastrous and expensive breakdowns in the electronic equipment.
Many service providers in some developing countries when installing equipment even indoors do not wish to or can not afford to provide this costly form of temperature control system yet still require the highest degree of reliability possible from their equipment.